Applied Mechanics and Materials Vols. 548-549

Abstract: The bidirectional DC-DC converter can achieve energy storage and transfer by adjusting the magnitude and direction of the current, which is widely used in the DC interconnect micro-grid system and battery energy management system. In the current tracking control of the bidirectional DC-DC converter, the switching loss can be significantly reduced under the Zero Voltage Switching (ZVS) condition. In this situation, the paper firstly establishes the model of switching progress. Considering the ZVS constraints, the model can be described as piecewise linear equations. Secondly, based on the piecewise model, the model predictive controller is constructed. By solving a constrained optimal problem, the switching time forecast in the ZVS condition is obtained to realize the current tracking. Moreover, the derivation of boundary conditions is presented. Finally, a simulation is presented to validate the proposed model and control method.

Abstract: In the Signal-collecting in Sensorless PMSM Parameters Identification research appeared Voltage signal and Current signal are not common ground. In-depth study the problem and solved it. In order to solve the problem that Voltage signal and Current signal are not common ground, using Linearity of coupler element, Through the optical coupling element not only achieve a high and low pressure isolation and through a series of analog circuit to achieve the output terminal to the common ground. Input pressure value falls below the voltage data acquisition card allows the range of values. We verify the validity of this approach by multisim simulation software to.

Abstract: A parametric model of a kind of low-voltage circuit breaker was set up by virtual prototyping technology software ADAMS, and the simulation of the low-voltage circuit breaker system’s dynamic characteristics was successfully run to confirm the parametric model. Because it was easy for contact heads to produce arc during closing, the power spring system was designed and researched in order to obtain the parametric sensitivities. Based on the difference of parametric sensitivities, the rotational angular velocity of the moving contact heads was regarded as the objective function, and the optimization design of circuit breaker power system was completed. Optimized system ensured reliable contact and shortened the arc time of the static and dynamic contact heads during closing, avoiding phenomenon as rebound repeatedly beating of the contact heads, continued arcing and temperature sharp rising, etc. The analysis had guide significance for improving the safe reliability and operating life of the low-voltage circuit breaker, and provided a good platform for the further produce development and optimization design.

Abstract: In order to analyze the characteristics of tidal current power generation system, we measured the output power according to the stream velocity by a water tunnel system and a simulation in MATLAB/Simulink. The water tunnel system consisted of impeller tidal flow transducer and permanent magnet synchronous generator (PMSG) with rotor in the water. The simulation consisted of PMSG, the tidal current turbine, and Back-to-Back converter. Also, we simulated the characteristics of output power according to the change of blade radius and velocity.

Abstract: A new method of fault diagnosis for power networks by using the combinatorial cross entropy (CCE) algorithm is proposed. The research contents in this paper mainly contain the two parts: transmission network fault diagnosis and distribution network fault location. For transmission network, the optimization model is built by considering the relationship among fault elements, action information of protective relays and circuit breakers. For distribution network, constructing fault location model according to the logic relationship between fault current and equipment condition. The optimal solution of two models are solved by CCE algorithm, then fault element (s) in transmission network and fault section (s) in distribution network can be identified by the optimal solution. Various fault conditions are simulated in test system and the results show that conclusions obtained by proposed method are correct, which prove CCE algorithm diagnose fault effectively.

Abstract: Sediment microbial fuel cells (SMFCs) produce electricity through the bacterial oxidation of organic matter contained in the sediment, but the power density is limited and needs to be improved. In this study, a new design of a fined-type cathode with carbon cloth embedded partly, as opposed to completely, in SMFCs were utilized. As a result, the design allowing the cathode to contact air will have a positive effect on the power performance and decrease the resistance of the inner system. The power density in the cases where the cathode was about half soaked was about two folds the case where it was soaked completely. Furthermore, SMFCs would also be seen as a driving force in hastening the COD removal because it was about 1.92-folds the COD removal of the cases where SMFCs where not present. These findings can be applied to sewage treatment and improving the power performance in SMFCs.

Abstract: While lots of works have been done regarding low penetration photovoltaic (PV), high penetration PV has not been well investigated in the literature, especially the issues such as supply reliability and power utilization efficiency. In this paper, we first present a modified microgrid model for high penetration PV. Within the architecture of the proposed microgird, we then design a trust based active power matching scheme for efficient power usage. Power factor regulation is also used to keep the microgird running steadily. Finally, simulation results are shown to verify the effectiveness of the proposed scheme.

Abstract: Nuclear power as an important energy which benefits human being,is being more and more widely used in many countries all over the world. Under the condition of information war, threat to nuclear power plant security from precision weapon and terrorist attack is serious. This paper analyzes major threats nuclear power plant be facing to in wartime such as obvious exposure symptoms, limited own protections and large impact on the war potential. Then several main methods are discussed to strengthen safety protection of nuclear power plant. Firstly, strive to improve the early warning ability of nuclear power plant. By this means, more time can be obtained to make nuclear power plant protection to prepare. Secondly, counterattacks, interference and disguise simultaneously should build another effective barrier. In the last, it is considered that research on protection and rescue of nuclear power station should be strengthened also.

Abstract: Abstract: Analyzing the rules of microgrid operation based on the design principle and engineering philosophy, and then defining seven microgrid operation states included: grid-tied state, and/off state, off-grid state, off/and state, fault state, power-latch state and shutdown state. Based on these seven modes, the different control strategy will be set out. These seven strategies can be integrated and be used to control the microgrid together. So we can gain the maximum efficiency of the microgrid through that above. At the same time, the appropriate control mode will be selected to guarantee the microgrid can be switched from one mode to another smoothly.. Above all, the microgrid can operate reliably through the integrated control strategy.

Abstract: Solar-led streetlight is a hotspot in photovoltaic lighting at present, it combines solar energy with HB LEDs (High Brightness Light Emitting Diodes) called the fourth generation of light source to improve the conventional streetlight in several aspects. Due to the clean nature of solar energy, and the highly efficient energy conversion of the PV module and very long operating life of the HB LED, the solar-LED streetlight, compared to traditional streetlight, can save electricity remarkably, thus abating greenhouse gas emission. During the photovoltaic lighting system, MPPT technology is generally used with the aim of maximizing the solar panel output power from beginning to the end. Therefore, if the controller combines MPPT technology with the traditionally constant-voltage charging technology, the charge efficiency will be greatly increased. While, for the discharge issue, people hope to modulate the brightness of streetlight so as to decrease the electricity consume.